Automobile hood

ABSTRACT

In an automobile hood, sufficient panel rigidity and dent resistance of a panel are secured while achieving weight reduction. An automobile hood having panel, reinforcing member and joint that joins the panel and the reinforcing member such that the reinforcing member includes a structure formed from a plurality of units having hexagonal annular shape disposed in a close-packed arrangement. Floor of the unit has an annular end part. All of annular end part is located between first circle and second circle wherein first circle is inscribed within a first ridge line overlapping with an outer end part of the floor. Second circle is concentric with first circle and has a radius that is 60% of a radius of the first circle. Width of upper face of floor is 2 mm or more over the entire area of the annular end part in the circumferential direction of the annular end part.

TECHNICAL FIELD

The present disclosure relates to an automobile hood.

BACKGROUND ART

Automobile hoods are known (for example, see Patent Documents 1 and 2).

Patent Document 1 discloses a hood panel structure for a vehicle. Theprincipal purpose of the hood panel structure is to reduce the degree ofinjury to a pedestrian if the pedestrian collides with the hood panel.

Patent Document 2 discloses a hood for an automobile as exteriorequipment for an automobile. The principal purpose of the hood for anautomobile is to absorb the energy of contact when a pedestrian comesinto contact with the hood for an automobile, by only deforming by asmall amount in the inward direction of the automobile.

LIST OF PRIOR ART DOCUMENTS Patent Document

Patent Document 1: JP2005-193863A

Patent Document 2: JP2017-1553A

SUMMARY OF INVENTION Technical Problem

There is a demand for the weight of automobile hoods to be reducedfurther and also for the panel rigidity and the dent resistance ofautomobile hoods to be improved. However, for example, if a panel of anautomobile hood made of a steel sheet is made thinner than 0.6 mm inorder to reduce the weight, both the panel rigidity and the dentresistance will decrease to an extent that cannot be ignored.

Patent Document 1 and Patent Document 2 do not disclose any mattersregarding problems or structures from the viewpoint of securing bothsufficient panel rigidity and sufficient dent resistance while achievinga weight reduction.

One objective of the present disclosure is, with respect to anautomobile hood, to secure sufficient panel rigidity and dent resistanceof a panel while achieving a weight reduction.

Solution to Problem

The gist of the present disclosure is an automobile hood which isdescribed hereunder.

An automobile hood, including:

a panel,

a reinforcing member, and

a joint that joins together the panel and the reinforcing member,

wherein:

the reinforcing member includes a structure formed from a plurality ofunits having a hexagonal annular shape disposed in a close-packedarrangement;

the unit has a floor, an inclined wall, and a top plate;

the floor is adjacent to the panel;

the top plate and the panel are separated from each other;

the inclined wall is between the floor and the top plate;

a hexagonal annular ridge line of the unit is between the floor and theinclined wall;

the floor has an annular end part which is centered on a center of theannular unit;

all of the end part is between a first circle which is inscribed withinthe ridge line, and a second circle which is concentric with the firstcircle and which has a radius that is 60% of a radius of the firstcircle;

the floor includes a floor surface as a face which faces the panel; and

a width of the floor surface is 2 mm or more over an entire area of theannular end part in a circumferential direction of the annular end part.

(2) The automobile hood according to the above (1), wherein a distancebetween a corner of the hexagonal ridge line and the annular end part isgreater than a distance between a center of one side of the ridge lineand the annular end part.

(3) The automobile hood according to the above (1) or (2), wherein theend part is circular.

(4) The automobile hood according to the above (1) or (2), wherein theend part is hexagonal.

(5) The automobile hood according to the above (1) or (2), wherein theend part is dodecagonal.

(6) The automobile hood according to any one of the above (1) to (5),wherein:

the panel is a steel sheet, and

a sheet thickness of the panel is within a range of 0.35 mm to 0.60 mm.

(7) The automobile hood according to any one of the above (1) to (5),wherein:

the panel is an aluminum alloy sheet, and

a sheet thickness of the panel is within a range of 0.50 mm to 1.00 mm.

Advantageous Effects of Invention

According to the present disclosure, in an automobile hood, sufficientpanel rigidity and dent resistance of a panel can be secured whileachieving a weight reduction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic exploded perspective view of an automobile hoodaccording to one embodiment of the present disclosure.

FIG. 2 is a plan view of a reinforcing member of the automobile hood.

FIG. 3 is a schematic cross-sectional view along a line III-III in FIG.2.

FIG. 4 is a cross-sectional view along a line IV-IV in FIG. 2, in whichillustration of a portion that appears to the rear of the cross-sectionis omitted.

FIG. 5 is a view in which one part of FIG. 3 is enlarged.

FIG. 6 is a plan view in which the circumference of one unit of theautomobile hood is enlarged.

FIG. 7A is a view illustrating, in a simplified form, the circumferenceof one unit that is illustrated in FIG. 6.

FIG. 7B is a view illustrating one portion extracted from FIG. 7A.

FIG. 8A is a conceptual side view for describing a case where a maximumsupport span of a panel supported by an annular end part is too long.

FIG. 8B is a conceptual side view for describing a case where a maximumsupport span of a panel supported by an annular end part is appropriate.

FIG. 8C is a conceptual side view for describing a case where a maximumsupport span of a panel supported by an annular end part is too short.

FIG. 9A is a schematic plan view illustrating the principal part of afirst out-of-range example.

FIG. 9B is a schematic plan view illustrating the principal part of asecond out-of-range example.

FIG. 10A is a view illustrating, in a simplified form, the circumferenceof one unit according to a first modification.

FIG. 10B is a view illustrating one portion extracted from FIG. 10A.

FIG. 11A is a view illustrating, in a simplified form, the circumferenceof one unit according to a second modification.

FIG. 11B is a view illustrating one portion extracted from FIG. 11A.

FIG. 12 is a view for describing one example of the arrangement ofjoints in an automobile hood.

FIG. 13 is a conceptual plan view illustrating the principal part of athird modification of the present disclosure, and shows locations atwhich joints are provided.

FIG. 14 is a conceptual plan view illustrating the principal part of afourth modification of the present disclosure, and shows locations atwhich joints are provided.

FIG. 15 is a conceptual plan view illustrating the principal part of afifth modification of the present disclosure, and shows locations atwhich joints are provided.

FIG. 16 is a schematic plan view illustrating shapes A to D with respectto an annular end part.

FIG. 17 is a schematic plan view illustrating shapes E to H with respectto an annular end part.

FIG. 18 is a schematic plan view illustrating shapes I, J and K withrespect to an annular end part.

DESCRIPTION OF EMBODIMENTS

Hereunder, first, the circumstances leading to the conception of thepresent disclosure will be described, and then an embodiment will bedescribed in detail.

[Circumstances Leading to Conception of Present Disclosure]

In the present description, the term “panel rigidity” refers to, in acase where a force from outside acts on a press-formed product, forexample, a panel on the outer side of an automobile hood, which has acomparatively moderately curving surface and in which the surface areais extremely large relative to the sheet thickness, the rigidity of thepanel in question. The panel rigidity corresponds to a feeling ofelastic resistance or a sensation of deflection deformation when thepanel is pressed with a hand. This characteristic is usually representedby the deflection when a load is applied, and the smaller the deflectionis when a constant load is applied, the higher the panel rigidity is.

In the present description, the term “dent resistance” refers to thedifficulty for an indentation (dent) to be left after removing the loadin a case where a localized load is applied to a panel for some reason.In the case of the body of an actual automobile, such dents occur whenan outer panel of a door or the like is strongly pressed with a fingeror the palm of a hand, or when the automobile body is hit by a flyingstone while travelling and the like. A dent is formed as a result of aplace on the panel at which a load has been applied plasticallydeforming. Therefore, when the strain on the panel at a time that a loadis applied thereto reaches a certain magnitude, the strain remains evenafter the load is removed, resulting in a dent. The minimum value of aload that causes a certain residual strain in the panel is referred toas the “dent load”, and the larger the dent load is, the better the dentresistance is.

In an automobile hood, the thinner the sheet thickness of a panel ismade, the more both the panel rigidity and the dent resistance decrease.Further, with regard to automobile hoods, it cannot be said thatconventionally improvements have been made mainly from the viewpoint ofsufficiently securing both panel rigidity and dent resistance whileachieving a weight reduction.

Weight reduction, panel rigidity and dent resistance will now bedescribed more specifically. First, the definition of panel rigidity isas described above. That is, the term “panel rigidity” refers to thedegree of inflexibility of a panel. For example, when a panel of anautomobile hood is pressed with a hand, it is difficult for the panel todeflect if the panel rigidity is high. The definition of dent resistanceis also as described above. That is, the term “dent resistance” refersto the degree to which it is difficult to form a dent flaw. For example,when a pebble hits a panel, if the dent resistance is low, a dent flawwill be easily formed in the panel.

In recent years, in order to reduce the weight of automobiles, thestrength of members constituting the automobiles is being increased. Ingeneral, if the strength (tensile strength) of a member is increased,the walls of the member can be made thinner. It is considered that, as aresult, the weight of the member can be reduced. However, it is not thecase that such kind of weight reduction achieved by increasing thestrength simply holds true for an exterior material such as a panel ofan automobile. This is because the panel rigidity and the dentresistance which are required for an exterior material of an automobileare not determined only by the strength of the exterior material.

The aforementioned occurrence of deflection in which the panel rigidityin an outer panel of an automobile hood is reflected depends mainly onthe modulus of elasticity and sheet thickness of the panel. Further,with respect to steel sheets, there is no difference in the value of theYoung's modulus between a low-strength material and a high-strengthmaterial. Therefore, even if a low-strength material is simply replacedwith a high-strength material, the panel rigidity does not improve. Onthe other hand, when a low-strength material is replaced with ahigh-strength material, the dent resistance that is one kind ofresistance to plastic deformation improves. However, the influence whichthe steel material strength has on the dent resistance is much less thanthe influence which the sheet thickness of the panel has on the dentresistance. Hence, even if a low-strength material is simply replacedwith a high-strength material, a significant improvement in the dentresistance cannot be expected.

Further, with respect to the relation between the panel rigidity anddent resistance of the panel and the sheet thickness of the panel, asdescribed above, when the panel is made thinner, both the panel rigidityand the dent resistance decrease. Consequently, there is a limit to theamount of weight reduction that can be achieved while securing the panelrigidity and the dent resistance. The thickness of a panel that isconsidered to be such a limit is around 0.65 mm in the case of a panelmade of a steel sheet. However, it is desired to make such automobilepanels thinner than 0.65 mm in order to reduce the weight.

However, at the present time, the sheet thickness of panels is not beingmade thinner than 0.65 mm. This is because the thinner the sheetthickness of a panel is made, the greater the deflection of the panelwill be when the panel is touched with a hand in order to perform waxingor the like. In other words, it is because a high-quality feeling willno longer be felt from the automobile. On the other hand, in order tosuppress such kind of deflection and reduce the degree of injury to apedestrian at the time of a collision, attachment of a reinforcingmember to a panel on a side which is on the inner surface side of avehicle has been performed up to now.

In order to improve the panel rigidity of a panel using a reinforcingmember, it is preferable to increase the rigidity of the reinforcingmember. However, if the sheet thickness of a reinforcing member isincreased in order to increase the rigidity of the reinforcing member,the reinforcing member will become heavy, which is not preferable forreducing the weight of the automobile hood. Further, it is notnecessarily the case that the dent resistance will be improved even ifthe rigidity of the reinforcing member is increased. Because of theexistence of such problems, even when a reinforcing member is simplyused, it is difficult to secure both panel rigidity and dent resistancewhile also reducing the weight of the automobile hood.

As the result of diligent research, the inventors of the presentapplication came to pay attention to the aforementioned problems, andconducted additional diligent research. The inventors of the presentapplication then conceived of adopting a honeycomb structure as areinforcing member of an automobile hood, in consideration of thebalance between strength and weight. However, simply adopting ahoneycomb structure is insufficient for securing both high panelrigidity and high dent resistance. This is because the shorter thelength of one side is in a hexagonal annular unit constituting thehoneycomb structure, the shorter the support span of the panel can bemade, which is preferable for improving the panel rigidity. On the otherhand, the shorter that the aforementioned length of one side is, thesmaller the tolerance of the elastic deflection of the panel will be,and hence the more the dent resistance will decrease. In addition, theshorter the length of one side is, the higher the mass density of thereinforcing member will be, and the heavier the reinforcing member willbecome. By continuing to conduct diligent research even after conceivingof forming a reinforcing member with a honeycomb structure, theinventors of the present application obtained the aforementionedfindings for the first time. Subsequently, based on these findings, theinventors of the present application conceived of a structure whichsatisfies all of the requirements with respect to weight reduction,securing panel rigidity, and securing dent resistance. That is, theinventors of the present application arrived at the present disclosure,for which one example is described hereunder.

Description of Embodiment

Hereunder, an embodiment of the present disclosure is described whilereferring to the accompanying drawings.

FIG. 1 is a schematic exploded perspective view of an automobile hood 1according to one embodiment of the present disclosure. FIG. 2 is a planview of a reinforcing member 3 of the automobile hood 1. FIG. 3 is aschematic cross-sectional view along a line in FIG. 2. FIG. 4 is across-sectional view along a line IV-IV in FIG. 2, in which illustrationof a portion that appears to the rear of the cross-section is omitted.Note that, in FIG. 3 and FIG. 4, a panel 2 that does not appear in FIG.2 is indicated by a chain double-dashed line that is a virtual line.

FIG. 5 is a view in which one part of FIG. 3 is enlarged. FIG. 6 is aplan view in which the circumference of one unit 7 of the automobilehood 1 is enlarged. In FIG. 6, units 7 that are other than a single unit7 at the center are illustrated using thinner lines than the centralunit 7 so as to be easily distinguished from the central unit 7. FIG. 7Ais a view illustrating, in a simplified form, the single unit 7illustrated in FIG. 6. FIG. 7B is a view illustrating one portionextracted from FIG. 7A. Hereinafter, unless otherwise specified, theembodiment will be described with reference to FIG. 1 to FIG. 7B asappropriate.

The automobile hood 1 is a front hood provided at the front part of anautomobile, and is also called a “bonnet”. An automobile in which theautomobile hood 1 is provided is, for example, a passenger vehicle. Asedan-type passenger vehicle, a coupe-type passenger vehicle, ahatchback-type passenger vehicle, a minivan-type passenger vehicle, anSUV (Sport Utility Vehicle) type passenger vehicle, and the like can bementioned as examples of the passenger vehicle.

Note that, in the present description, the terms “front”, “rear”,“left”, “right”, and “upper” and “lower” are used taking a time when theautomobile hood 1 is mounted to an automobile and the automobile hood 1is closed as the basis. The term “front” refers to the direction inwhich the automobile advances. The term “rear” refers to the directionin which the automobile reverses. The term “right” refers to the turningdirection of the automobile when the automobile which is advancing turnsto the right. The term “left” refers to the turning direction of theautomobile when the automobile which is advancing turns to the left.Further, in the present embodiment, the vehicle width direction of theautomobile to which the automobile hood 1 is mounted is referred to as“vehicle width direction X”. Further, the vehicle length direction ofthe automobile to which the automobile hood 1 is mounted is referred toas “vehicle length direction Y”. Furthermore, the vehicle heightdirection of the automobile to which the automobile hood 1 is mounted isreferred to as “vehicle height direction Z”.

The automobile hood 1 has a panel 2, a reinforcing member 3, and a joint4 that joins together the panel 2 and the reinforcing member 3.

In the automobile hood 1, the panel 2 is a portion that constitutes apart of the outer surface of the automobile. The panel 2 is formed of,for example, a metal material such as a mild steel sheet or ahigh-tensile strength steel sheet. As an example of the high-tensilestrength steel sheet, a steel sheet having a tensile strength of 340 MPaor more can be mentioned, and a steel sheet having a tensile strengthwithin a range of 440 MPa to 590 MPa can be mentioned as a preferableexample. The panel 2 is formed, for example, by subjecting a singlesteel sheet to press working or the like. A sheet thickness t1 of thepanel 2 (thickness of the steel sheet) is set to 0.60 mm or less,preferably is set to 0.50 mm or less, and more preferably is set to 0.40mm or less. The lower limit of the sheet thickness t1 of the panel 2 ispreferably 0.35 mm. The sheet thickness t1 of the panel 2 is, forexample, within the range of 0.35 mm to 0.60 mm. The thinner the sheetthickness of the panel 2 is made in this way, the lighter the automobilehood 1 can be made.

The panel 2 may be an aluminum alloy sheet. In this case, the sheetthickness of the panel 2 is set so as to obtain equivalent values fromthe viewpoint of panel rigidity and dent resistance with respect to thesheet thickness of the panel 2 that is made of a steel sheet. Morespecifically, the panel rigidity depends on the Young's modulus of thematerial and the sheet thickness. Further, the dent resistance dependson the yield stress of the material and the sheet thickness. Hence, ifthe sheet thickness of the panel 2 made of an aluminum alloy sheet isapproximately 1.5 to 1.6 times larger than the sheet thickness of thepanel 2 made of a steel sheet, it can be said that the panel 2 that ismade of an aluminum alloy and the panel 2 that is made of a steel sheetare equivalent from the viewpoint of panel rigidity and dent resistance.

In a case where the panel 2 is an aluminum alloy sheet, an aluminumalloy sheet having a tensile strength of 250 MPa or more, preferably, analuminum alloy sheet having a tensile strength of 300 MPa to 350 MPa,can be mentioned as an example thereof. The sheet thickness t1 of thepanel 2 in this case (thickness of the aluminum alloy sheet) is set to1.00 mm or less, preferably is set to 0.80 mm or less, and morepreferably is set to 0.64 mm or less. The lower limit of the sheetthickness t1 of the panel 2 is preferably 0.50 mm. The sheet thicknesst1 of the panel 2 is, for example, within the range of 0.50 mm to 1.00mm.

There are no particular restrictions with regard to the shape of thepanel 2. Note that, in the present embodiment, the panel 2 has a shapein which the central portion is upwardly convex in the height directionZ.

The reinforcing member 3 reinforces the panel 2 by being joined to anundersurface 2 a of the panel 2. By this means, the reinforcing member 3increases both the panel rigidity and the dent resistance of the panel2. That is, in the present embodiment, the panel rigidity and the dentresistance of the panel 2 are secured not by increasing the sheetthickness of the panel 2, but rather are secured by the reinforcingmember 3. The reinforcing member 3 is formed, for example, of a metalmaterial such as a steel sheet. The reinforcing member 3 is formed, forexample, by subjecting a single steel sheet to press working. Thereinforcing member 3 may be an integrally formed product, or may beformed by joining a plurality of members together. In the presentembodiment, the reinforcing member 3 is an integrally formed product. Asheet thickness t2 of the reinforcing member 3 (thickness of the steelsheet) is preferably within the range of 0.3 mm to 0.8 mm. The upperlimit of the sheet thickness t2 of the reinforcing member 3 ispreferably 0.6 mm. The sheet thickness t2 of the reinforcing member 3may be less than the sheet thickness t1 of the panel 2, may be the sameas the sheet 1thickness t1 of the panel 2, or may be greater than thesheet thickness t1 of the panel 2.

The reinforcing member 3 may be an aluminum alloy sheet. In this case,the sheet thickness of the reinforcing member 3 is set to an equivalentvalue from the viewpoint of panel rigidity and dent resistance withrespect to the sheet thickness of the reinforcing member 3 that is madeof a steel sheet. Therefore, similarly to the case of the panel 2, ifthe sheet thickness of the reinforcing member 3 made of an aluminumalloy is approximately 1.5 to 1.6 times larger than the sheet thicknessof the reinforcing member 3 made of a steel sheet, it can be said thatthe reinforcing member 3 made of an aluminum alloy and the reinforcingmember 3 made of a steel sheet are equivalent from the viewpoint ofpanel rigidity and dent resistance. In a case where the reinforcingmember 3 is made of an aluminum alloy, the sheet thickness t1 of thereinforcing member 3 (thickness of the aluminum alloy sheet) is withinthe range of 0.4 to 1.3 mm. The upper limit of the sheet thickness t2 ofthe reinforcing member 3 is preferably 1.0 mm.

The reinforcing member 3 has an outer circumferential portion 5, and ahoneycomb structural body 6 disposed so as to be surrounded by the outercircumferential portion 5.

The outer circumferential portion 5 is a portion that is disposed alongan outer circumferential part of the panel 2. When the panel 2 closesthe engine room, an outer circumferential edge portion 5 a of the panel5 is received by the automobile body (not illustrated) together with theouter circumferential portion of the panel 2. By this means, a load thatacts on an upper face 2 b of the panel 2 is received by the automobilebody through the reinforcing member 3. An inner circumferential edgeportion 5 b of the outer circumferential portion 5 is a portion that isarranged so as to surround the honeycomb structural body 6 and is joinedto the honeycomb structural body 6.

The honeycomb structural body 6 has a three-dimensional structure whichis provided in order to receive a load acting on the upper face 2 b ofthe panel 2. The honeycomb structural body 6 is formed by combiningmembers that have a V-shaped cross section (hat-shaped cross section).

The honeycomb structural body 6 has a plurality of units 7, and aplurality of sub units 8 that are adjacent to the inner circumferentialedge portion 5 b of the outer circumferential portion 5 and continuouswith the outer circumferential portion 5.

The unit 7 which is adjacent to the outer circumferential portion 5 ofthe reinforcing member 3 is connected to the outer circumferentialportion 5 directly or through the sub unit 8.

The sub unit 8 has a configuration equivalent to a configuration inwhich one portion of the unit 7 has been cut off in the circumferentialdirection of the hexagonal unit 7. The sub unit 8 has a side portionthat is similar to a side portion 10 of the unit 7 that is describedlater. The side portion is continuous with the inner circumferentialedge portion 5 b of the outer circumferential portion 5.

Each unit 7 is formed in a hexagonal annular shape in plan view in thevehicle height direction Z. Hereinafter, when simply the term “planview” is used, it means a plan view in the vehicle height direction Z.In the present embodiment, each unit 7 is formed in the shape of asubstantially regular hexagon. The term “regular hexagon” means ahexagon in which the lengths of the respective sides are equal and theinterior angles are also a constant angle of 120 degrees. Further, inthe present description, the term “substantially regular hexagon” refersto a hexagon that can be treated as a regular hexagon from the viewpointof the panel rigidity and the viewpoint of the dent resistance of thepanel 2. The respective units 7 are formed so that the shape of eachunit 7 is substantially the same. Note that, the term “substantially thesame” in this case indicates that the configuration is the same exceptin the respect that the shape of each unit 7 is caused to match a shapewhich matches the curved shape of the panel 2.

Each unit 7 may also be formed in the shape of a hexagon that is otherthan a regular hexagon. Examples of a hexagon other than a regularhexagon that can be mentioned include a hexagon in which the lengths ofthe respective sides are not uniform, and a hexagon in which theinterior angles are not uniform at 120 degrees. Examples of a hexagon inwhich the lengths of the respective sides are not uniform that can bementioned include a hexagon in which the length of a front end side andthe length of a rear end side are set to a predetermined first length,and which has four sides whose lengths are each set to a predeterminedsecond length that is different from the first length.

The honeycomb structural body 6 has a structure formed from a pluralityof the units 7 having a hexagonal annular shape disposed in aclose-packed arrangement. In this case, the term “close-packed” meansthat, in a case where the honeycomb structural body 6 has other units 7to which the respective side portions 10 of a given unit 7 are adjacent,the given unit 7 is disposed without a gap existing between given unit 7and one side portion 10 of each of the relevant other units 7.Specifically, each unit 7 is partitioned off from the other units 7within a top plate 13. As illustrated in FIG. 6, a front end 13 b of thetop plate 13 forms a boundary of the top plate 13 that includes thefront end 13 b. The boundary is formed in a hexagonal shape in planview. By having such a structure formed from the units 7 disposed in aclose-packed hexagonal arrangement, the honeycomb structural body 6 canwithstand loads in substantially the same manner from all directionsincluding the vehicle height direction Z over the whole area in planview.

In the present embodiment, the plurality of the units 7 are formedsymmetrically in the vehicle width direction X as a whole. Specifically,in the present embodiment, three of the units 7 are arranged side byside in the front-to-rear direction at the center in the vehicle widthdirection X. Further, in plan view, the plurality of units 7 arearranged symmetrically in the vehicle width direction X with referenceto a virtual line A1 extending in the front-to-rear direction throughthe center of the aforementioned three units 7 in the vehicle widthdirection X. The arrangement of the units 7 is not limited to thisstructure, and because the panel rigidity, the dent resistance and themass do not depend on the direction of the units 7, there is noconstraint on the direction of the units 7.

In the present embodiment, in the direction toward the right side fromthe aforementioned three units 7 arranged at the central position in thevehicle width direction X are provided, in the following order, fourunits 7 which are arranged side by side in the vehicle length directionY, a further three units 7 which are arranged side by side in thevehicle length direction Y, a further two units 7 which are arrangedside by side in the vehicle length direction Y, and a further two units7 which are arranged side by side in the vehicle length direction Y.Furthermore, similarly to the foregoing arrangement, in the directiontoward the left side from the aforementioned three units 7 arranged atthe central position in the vehicle width direction X are provided, inthe following order, four units 7 which are arranged side by side in thevehicle length direction Y, further three units 7 which are arrangedside by side in the vehicle length direction Y, further two units 7which are arranged side by side in the vehicle length direction Y, andfurther two units 7 which are arranged side by side in the vehiclelength direction Y

Each of the units 7 has six of the side portions 10 (10 a to 10 f). Inthe present embodiment, in each of the units 7, a front side portion 10a and a rear side portion 10 d extend along the vehicle width directionX, respectively. Further, in each of the units 7, the remaining fourside portions 10 extend in a direction that inclines with respect to thevehicle length direction Y in plan view.

Each of the side portions 10 (10 a to 10 f) has a floor 11, a inclinedwall 12, and the top plate 13.

The floor 11 is adjacent to the panel 2, and in the side portion 10, thefloor 11 is a portion that is arranged closest to the panel 2. The floor11 is a strip-shaped portion. The floor 11 is a flange portion of theside portion 10, and the floors 11 of the six side portions 10 form ahexagonal flange. The inner end parts of six of the floors 11 constitutean annular end part 20 which is centered on the center of the annularunit 7 as a whole. The annular end part 20 of the unit 7 which is on thecenter side of the unit 7 is an end part that is arranged on the centerside of the unit 7. The annular end part 20 is centered on the center ofthe unit 7.

In a cross section (cross section illustrated in FIG. 5) orthogonal tothe longitudinal direction of the side portion 10, an outer end part 11c of the floor 11 is the intersection point between a virtual line V1including an upper face 11 b (rectilinear portion) of the floor 11 and avirtual line V2 including an intermediate portion (rectilinear portion)of an upper side face 12 a of the inclined wall 12. The intersectionpoint between the virtual lines V1 and V2 is the outer end part 11 c andis also a first ridge line 31. In a case where the floor 11 and theinclined wall 12 are connected in a curved shape as in the presentembodiment, the outer end part 11 c is a virtual end part. That is, inthe present embodiment, the first ridge line 31 is a virtual line. Onthe other hand, in a case where the floor 11 and the inclined wall 12are connected in a linearly pointed shape, the outer end part 11 c isthe connecting point between the floor 11 and the inclined wall 12. Inthis case, the first ridge line 31 is an actual line.

In the present embodiment, the first ridge line 31 is a hexagonalannular ridge line in plan view. The first ridge line 31 is between thefloor 11 and the inclined wall 12. The first ridge line 31 is one partof the floor 11, and is also one part of the inclined wall 12. The firstridge line 31 is adjacent to the panel 2.

Each of the two end parts in the longitudinal direction of the floor 11is formed in a curved shape in plan view, and smoothly connects with thefloor 11 of an adjacent side portion 10. In each unit 7, the floor 11 ofat least some of the side portions 10 is adhered to the joint 4 at theupper face 11 b as the floor surface, and is adhered to the panel 2through the joint 4. In the floor 11, the upper face 11 b is a facewhich faces the undersurface 2 a of the panel 2.

In the present embodiment, a length L1 of one side of the first ridgeline 31 is set to a length that is 40 mm or more and 75 mm or less. Ifthe length L1 of one side of the first ridge line 31 is less than theaforementioned lower limit, the span over which one unit 7 supports thepanel 2 will be short and the panel rigidity can be increased. However,the tolerance of deflection of the panel 2 will be small, and the dentresistance will decrease. In addition, the number of hexagonal annularunits 7 disposed in a close-packed arrangement will be too large, and asa result the reinforcing member 3 will be heavy. On the other hand, ifthe length L1 of one side of the first ridge line 31 is more than theaforementioned upper limit, the span over which one unit 7 supports thepanel 2 will be too long, and it will be difficult to secure sufficientpanel rigidity. By setting the length L1 of one side of the first ridgeline 31 within the aforementioned range, sufficient panel rigidity andsufficient dent resistance can be secured while lightening thereinforcing member 3. Hence, in the automobile hood 1, sufficient panelrigidity and dent resistance can be secured in the panel 2 whileachieving a reduction in the weight of the panel 2.

A width W1 (width at a cross section orthogonal to the longitudinaldirection of the side portion 10) of the upper face 11 b of the floor 11is the distance between an inner end part 20 and the outer end part 11 cof the floor 11. The width W1 is 2 mm or more over the whole area of theannular end part 20 in the circumferential direction of the annular endpart 20. In order to both reduce the weight of the automobile hood 1 andimprove the dent resistance of the panel 2 in a compatible manner, it isnecessary that, as described above, the width W1 of the upper face 11 bof the floor 11 is 2 mm or more over the entire circumference area ofthe annular end part 20. If, for example, the width W1 were less than 2mm at a central portion in the longitudinal direction of the sideportion 10, it would be easy for a deflection to occur in the panel 2 ata time when a comparatively low load as a load P1 acts on the panel 2 ata position C1 on the center position of the unit 7. Therefore, the panelrigidity of the panel 2 would decrease.

Thus, the width W1 of the upper face 11 b of the floor 11 is set to, atlowest, 2 mm or more, and the center of the annular end part 20 iscaused to coincide with the center of the first ridge line 31. Asillustrated in FIGS. 7A and 7B, at each corner (apex) of the hexagonalfirst ridge line 31, the distance between the corner and the annular endpart 20 is a corner width W11 among the overall width W1. Further, oneach of the six sides of the first ridge line 31, the distance betweenthe center of one side of the first ridge line 31 and the annular endpart 20 is a center width W12 among the overall width W1. In the presentembodiment, the corner width W11> the center width W12. By adopting aconfiguration in which the corner width W11> the central width W12, itis possible to improve the panel rigidity and improve the dentresistance of the panel 2 while achieving a reduction in the weight ofthe reinforcing member 3 in a compatible manner.

In the present disclosure, in plan view, all of the annular end part 20is between a first circle CR1 and a second circle CR2. The first circleCR1 is a circle inscribed within the first ridge line 31. The secondcircle CR2 is concentric with the first circle CR1. Further, a secondradius r2 as the radius of the second circle CR2 is set to 60% (r2=0.6r1) of a first radius r1 as the radius of the first circle CR1.

In plan view, a center point P1 of the first circle CR1, a center pointP2 of the second circle CR2, a center point P3 (centroid) of the firstridge line 31 having a hexagonal annular shape, and a center point P20of the annular end part 20 coincide one another. In the presentembodiment, the annular end part 20 is formed in a perfect circle or asubstantially perfect circle that is centered on the center point P3 ofthe first ridge line 31 in plan view. In this case, the phrase“substantially perfect circle” means a case where, after performing ahole forming process on a blank or an intermediate formed product toserve as the reinforcing member 3 in order to form the annular end part20, the blank or the intermediate formed product is further subjected topress working or the like to form the unit 7, and consequently astrictly perfect circle is not formed.

By disposing the annular end part 20 between the first circle CR1 andthe second circle CR2 in plan view, of the entire unit 7, the inner sideportion of the annular end part 20 is hollow, and the reinforcing member3 can be reduced in weight. In addition, as illustrated in theconceptual side view of FIG. 8B, a maximum support span SP of the panel2 by the annular end part 20, that is, the diameter of the annular endpart 20, can be set to a value that is neither too large nor too small.Thus, the panel rigidity of the panel 2 can be sufficiently secured andthe dent resistance of the panel 2 can also be sufficiently secured.That is, it is possible to reduce the weight of the automobile hood 1,secure sufficient panel rigidity of the panel 2, and secure sufficientdent resistance of the panel 2 in a compatible manner. Therefore, evenwhen an indenter ID is pushed into the upper face 2 b of the panel 2, itis difficult for a dent to occur.

As described above, the annular end part 20 is between the first circleCR1 and the second circle CR2, and the width W1 is 2 mm or more over theentire upper face 11 of the floor 11,. According to this configuration,sufficient panel rigidity and dent resistance of the panel 2 can besecured while achieving a reduction in the weight of the automobile hood1.

Further, by making the annular end part 20 circular, a load from thepanel 2 can be received with a stable posture by the annular end part20, while also reducing the weight of the reinforcing member 3.

Note that, with regard to the annular end part 20, if even one portionof the annular end part 20 is larger than the first circle CR1, asillustrated in the conceptual side view of FIG. 8A, the maximum supportspan SP of the panel 2 supported by an annular end part 20′ (diameter ofthe annular end part 20′) will be too large. As a result, the area ofthe upper face 11 b of the floor 11 which can be adhered to the panel 2will be narrow. Consequently, the efficiency of the work of applying thejoint 4 to the floor 11 will be less efficient. In addition, the panelrigidity of the panel 2 will decrease. Furthermore, the dent resistancewill also decrease. More specifically, the dent resistance issignificantly affected by constraint of the surrounding part (annularend part 20′) with regard to the load that acts on the panel 2 when theindenter ID is pressed into the upper face 2 b of the panel 2.Therefore, in a case where the distance between the point of action of aload applied by the indenter ID and the surrounding constraint position(the annular end part 20′) is long as illustrated in FIG. 8A, when theload applied by the indenter ID is, for example, low (a time of a lowload), the deflection of the panel 2 becomes large. Consequently, it isdifficult to maintain the designed curved shape of the panel 2, andtherefore the dent resistance is liable to decrease and a dent DT isliable to occur.

On the other hand, if even one portion of an annular end part 20″ islocated further on the inner side than the second circle CR2, asillustrated in the conceptual side view of FIG. 8C, a hollow region ofthe inner side portion of the annular end part 20″ of the unit 7 issmall. Hence, the reinforcing member 3 becomes heavy, and the weightefficiency (the ratio of the reinforcing effect of the reinforcingmember 3 to the weight of the reinforcing member 3) deteriorates.Furthermore, the advantageous effect of improving the dent resistance ofthe panel 2 by means of the reinforcing member 3 also decreases. Morespecifically, as described above, the dent resistance is significantlyaffected by constraint of the surrounding part (the annular end part20″) with regard to the load from the indenter ID that acts on the panel2. Therefore, if the distance between the point of action of the loadfrom the indenter ID and the annular end part 20″ (constraint position)is too short as illustrated in FIG. 8C, when the load from the indenterID is, for example, low (a time of a low load), almost no deflection ofthe panel 2 occurs. As a result, localized stress arises at the point ofaction of the load from the indenter ID, and consequently a stress statethat is more than the yield load of the panel 2 is liable to occur and adent DT is liable to occur.

As is clearly illustrated in FIG. 7A and FIG. 7B, in the presentembodiment the annular end part 20 is an annular shape in plan view.Further, according to the present embodiment, a radius r20 of theannular end part 20 is 90% of the first radius r1. Note that, the radiusof the annular end part 20 may be 80% of the first radius r1, may be 70%of the first radius r1, or may be 60% of the first radius r1.

On the other hand, FIG. 9A and FIG. 9B illustrate two out-of-rangeexamples of the present disclosure. As a first out-of-range example, anexample in which a radius r20′″ of an annular end part 20′″ is 50% ofthe first radius r1 (FIG. 9A) can be mentioned, and an example in whicha radius r20′″ of an annular end part 20′″ is 20% of the first radius r1(FIG. 9B) can also be mentioned as an out-of-range example. Thus, in theout-of-range examples illustrated in FIG. 9A and FIG. 9B, the annularend parts 20′″ and 20′″ are located on the inner side of the secondcircle CR2.

In the above description a form in which the annular end part 20 is acircular shape is described. However, the configuration of the annularend part 20 is not limited to the configuration described above. Apolygon can be mentioned as an example in which the annular end part 20has a shape other than a circular shape in plan view. Note that, even ina case where the annular end part 20 is a polygon, the lower limit ofthe width W1 is 2 mm, and the entire area of the annular end part 20 isdisposed between the first circle CR1 and the second circle CR2.

A hexagon and a dodecagon can be mentioned as preferable examples of theaforementioned polygon in the present disclosure.

An example in which a hexagonal annular end part 20A is provided insteadof the circular annular end part 20 is illustrated as a firstmodification in FIG. 10A and FIG. 10B. The annular end part 20A is aregular hexagon or a substantially regular hexagon. In this case, thephrase “substantially regular hexagon” means a case where, afterperforming a hole forming process on a blank or an intermediate formedproduct to serve as the reinforcing member 3 in order to form theannular end part 20A, the blank or the intermediate formed product isfurther subjected to press working or the like to form the unit 7, andas a result the annular end part 20A does not become a strictly regularhexagon. In this first modification, each apex of the annular end part20A is disposed on a line segment L10A that links a center point P20 ofthe annular end part 20A and the midpoint of the corresponding side ofthe hexagonal first ridge line 31. Note that, each apex of the annularend part 20A may be disposed on a line segment that links the centerpoint P20 of the annular end part 20A and the corresponding apex of thehexagonal first ridge line 31.

By making the annular end part 20A circular in this way, a load from thepanel 2 can be received with a stable posture by the annular end part20A , while also reducing the weight of the reinforcing member 3.

An example in which a dodecagonal annular end part 20B is providedinstead of the circular annular end part 20 is illustrated as a secondmodification in FIG. 11A and FIG. 11B. The annular end part 20B is aregular dodecagon or a substantially regular dodecagon. In this case,the phrase “substantially regular dodecagon” means a case where, afterperforming a hole forming process on a blank or an intermediate formedproduct to serve as the reinforcing member 3 in order to form theannular end part 20B, the blank or the intermediate formed product isfurther subjected to press working or the like to form the unit 7, andas a result the annular end part 20B does not become a strictly regulardodecagon. In this second modification, two kinds of apexes AP1 and AP2are set as the apexes of the annular end part 20B. Each apex AP1 isdisposed on a line segment L10B that links a center point P20 of theannular end part 20B and a corresponding single apex of the hexagonalfirst ridge line 31. Further, each apex AP2 is disposed on a linesegment L20B that links the center point P20 of the annular end part 20Band the midpoint of the corresponding side of the hexagonal first ridgeline 31. Further, the apexes AP1 and the apexes AP2 are alternatelyarranged. In the second modification, a distance DS1B from the centerpoint P20 of the annular end part 20B to the respective apexes AP1 and adistance DS2B from the center point P20 of the annular end part 20B tothe respective apexes AP2 are the same. Note that, as long as theannular end part 20B is disposed between the first circle CR1 and thesecond circle CR2, the distance DS1B and the distance DS2B may bedifferent from each other.

By making the annular end part 20B dodecagon in this way, a load fromthe panel 2 can be received with a stable posture by the annular endpart 20B, while also reducing the weight of the reinforcing member 3.The foregoing is a description of the schematic configuration of thefloor 11.

As illustrated in FIG. 5, the inclined wall 12 extends downward from thefloor 11.

The inclined wall 12 is disposed between the floor 11 and the top plate13, and connects the floor 11 and the top plate 13. The inclined wall 12is provided over the entire area in the longitudinal direction of theside portion 10 in which the inclined wall 12 in question is provided.An angle θ1 that the inclined wall 12 forms with respect to the floor11, for example, an angle θ1 which is formed by the upper side face 12 aof the inclined wall 12 and the upper face 11 b of the floor 11, ispreferably set within a range of 40 degrees to 90 degrees. When theaforementioned angle θ1 is equal to or greater than the aforementionedlower limit, the inclined wall 12 can be sufficiently caused to functionas a pillar, and therefore a load transmitted from the panel 2 to thefloor 11 can be received by the inclined wall 12 with a small amount ofdeformation. Further, when the angle θ1 is less than or equal to theaforementioned upper limit, the unit 7 has a shape which graduallyincreases in width progressively in the downward direction (shape inwhich a distance between inclined walls 12 and 12 that face each otherwidens progressively toward the lower side in the vehicle heightdirection Z), and therefore the unit 7 is easy to be formed.

The length of the inclined wall 12 in the vehicle height direction Z isa component in the vehicle height direction Z of the distance betweenthe first ridge line 31 and a second ridge line 32, and is approximately16 mm in the present embodiment. In a cross section orthogonal to thelongitudinal direction of the side portion 10, the second ridge line 32is an intersecting point between a virtual line V3 which is a tangentialline to the apex of a lower side face 13 c of the top plate 13, and thevirtual line V2. The intersecting point between the virtual lines V2 andV3 is the second ridge line 32 and is also an inner end part 13 d of thetop plate 13. In a case where the inclined wall 12 and the top plate 13are connected in a curved shape as in the present embodiment, the secondridge line 32 is a virtual ridge line. On the other hand, in a casewhere the inclined wall 12 and the top plate 13 are connected in alinearly pointed shape, the second ridge line 32 is an actual line. Thesecond ridge line 32 can be said to be one part of the inclined wall 12,and can also be said to be one part of the top plate 13.

In the present embodiment, the second ridge line 32 is a hexagonalannular ridge line, similarly to the first ridge line 31. The secondridge line 32 is located at the outer circumference of the lower end ofthe inclined wall 12, and is separated from the panel 2. The first ridgeline 31 is one example of “a hexagonal annular ridge line between theinclined wall and the floor”, and is a ridge line at the end part on thefloor 11 side of the inclined wall 12. In the present embodiment, thefirst ridge line 31 and the second ridge line 32 are similar to eachother in plan view. In plan view, the overall length of the second ridgeline 32 is longer than the overall length of the first ridge line 31. Inthe vehicle height direction Z, the distance from the panel 2 to thesecond ridge line 32 is longer than the distance from the panel 2 to thefirst ridge line 31. Note that, the smaller the inclination angle θ1 ofthe inclined wall 12 is, the larger the ratio of the length of one sideof the second ridge line 32 to the length L1 of one side of the firstridge line 31 becomes. Therefore, the length of one side of the secondridge line 32 is preferably set to 40 mm or more and 95 mm or less.

In the present embodiment, the thickness (length in the vehicle heightdirection Z) of the unit 7 can be set by setting the length and theangle θ1 of the inclined wall 12. The floor 11 is continuous with theupper end of the inclined wall 12. The top plate 13 is continuous withthe lower end of the inclined wall 12. In a cross section orthogonal tothe longitudinal direction of the side portion 10, the floor 11 and theinclined wall 12 are continuous with each other in a smoothly curvingshape, and are connected in a form in which it is difficult for stressconcentration to occur. Similarly, the top plate 13 and the inclinedwall 12 are continuous with each other in a smoothly curving shape, andare connected in a form in which it is difficult for stressconcentration to occur. Note that, the floor 11 and the inclined wall 12may be connected in a pointed shape, and the inclined wall 12 and thetop plate 13 may be connected in a pointed shape.

In the unit 7, the top plate 13 is a portion that is farthest from thepanel 2. The top plate 13 is formed in a curved shape which is convex inthe downward direction, or is formed in a shape that extendsapproximately horizontally. The top plate 13 is provided over the entirearea in the longitudinal direction of the side portion 10 in which theinclined wall 12 in question is provided. In a cross section orthogonalto the longitudinal direction of the side portion 10, the floor 11, theinclined wall 12, and the top plate 13 are arranged in that order fromthe inner side to the outer side of the unit 7. The front end 13 b ofthe top plate 13 in one unit 7 is integral with the front end 13 b ofthe top plate 13 in an adjacent unit 7.

FIG. 12 is a view for describing one example of the arrangement of thejoints 4 in the automobile hood 1. Next, the joint 4 will be morespecifically described while referring mainly to FIG. 5 and FIG. 12. InFIG. 5, the joint 4 is indicated by hatching that represents a cutcross-section. In the present embodiment, the joint 4 is an adhesive. Amastic sealer (mastic adhesive) can be exemplified as the adhesive. Aresin-based adhesive can be exemplified as the mastic sealer. Theadhesive may have a property of being cured at normal temperature (forexample, 20 degrees Celsius), or may have a property of being cured byundergoing a heating process or a drying process.

The joint 4 is provided so as to sufficiently secure both panel rigidityand dent resistance while achieving a reduction in the weight of theautomobile hood 1. Specifically, the joint 4 is provided in at least twoof the side portions 10 that are parallel to each other among the sixside portions 10. In the present embodiment, in each of the units 7, thejoint 4 is provided in all of the six side portions 10. In the presentembodiment, on the upper face 11 b of the floor 11 of each side portion10, the joint 4 is provided over the entire area in the longitudinaldirection of the side portion 10, and the joints 4 provided on the sideportions 10 that are adjacent are integrated with each other. By thismeans, in the present embodiment, in each of the units 7, the joint 4 isa hexagonal shape.

A thickness t3 of the joint 4 is, for example, about several mms, and isan extremely large value relative to both the sheet thickness t1 of thepanel 2 and the sheet thickness t2 of the reinforcing member 3. Hence,the proportion that the joint 4 accounts for with regard to the materialcost and the weight of the automobile hood 1 cannot be ignored.Therefore, from the viewpoint of the material cost and also reducing theweight of the automobile hood 1, the joint 4 is preferably used in thesmallest possible amount. On the other hand, the joint 4 is also a loadtransmission portion that is provided for transmitting the load from thepanel 2 to the unit 7. Therefore, a more preferable usage form of thejoint 4 in each unit 7 can be defined from the viewpoint of achievingeach of a weight reduction, an improvement in the panel rigidity, and animprovement in the dent resistance.

FIG. 13 is a conceptual plan view illustrating the principal part of athird modification of the present disclosure, and shows locations wherethe joints 4 are provided. The following configuration that isillustrated in FIG. 13 can be mentioned as an example of the thirdmodification of the present embodiment. That is, the joint 4 is providedin some of the side portions 10 among the six side portions 10 (10 a to10 f) of each of the annular units 7. In this modification of thepresent disclosure, among the six side portions 10, the joint 4 isprovided in at least two side portions 10 that face each other inparallel and which are two side portions 10 that are separated from eachother. In each side portion 10 in which the joint 4 is provided, thejoint 4 extends in a linear stripe along the longitudinal direction ofthe side portion 10.

A length W2 of the joint 4 in plan view is set within the range of 20%to 100% of an overall length W3 of the floor 11 in the longitudinaldirection of the floor 11, and preferably is set within the range of 50%to 100%. In FIG. 13, an example is illustrated in which the length W2=the overall length W3. By making the length W2 of the joint 4 equal toor greater than the aforementioned lower limit, the bonding strengthbetween the floor 11 on which the joint 4 is provided and the panel 2can be sufficiently secured. In addition, in a case where a process isadopted that adheres the panel 2 and the floor 11 to each other byheating the joint 4, thermal distortion occurs in the panel 2 and thereinforcing member 3 due to the heating in the process for heating thejoint 4. However, by providing the joints 4 only on some of the six sideportions 10 of the unit 7, the aforementioned thermal distortion can bereduced.

As described above, in the third modification, in each unit 7, the joint4 is provided in some of the side portions 10 among the six sideportions 10, and the joint 4 is not provided in the remaining sideportions 10. The whole area of each of the remaining side portions 10directly faces the panel 2 vertically.

As illustrated in FIG. 13, four of the side portions 10 among the sixside portions 10 are joined to the joints 4, and are joined to the panel2 by the relevant joints 4. That is, the joint 4 is provided on twopairs of the side portions 10 that face each other in parallel in planview. The remaining two side portions 10 (two side portions 10 which arenot adjacent to each other) that are separated from each other are notprovided with the joint 4 and are directly adjacent to the panel 2(through only air).

More specifically, among the six side portions 10, the joint 4 isprovided on the front side portion 10 a and the rear side portion 10 dwhich extend in parallel with each other, and the right rear sideportion 10 c and the left front side portion 10 f which extend inparallel with each other. That is, in the unit 7, the joint 4 isprovided on each of four side portions 10 that exclude the right frontside portion 10 b and the left rear side portion 10 e. By this means, inthe honeycomb structural body 6, as illustrated by an arrow B1, a region14 in which joints are not set is provided in the direction from theleft rear toward the right front (toward the diagonally right frontside).

By means of this configuration, the honeycomb structural body 6 isprovided with a plurality of sets 15 of the joints 4 having a zigzagstripe shape extending from the left rear to the right front. Accordingto this kind of configuration of the honeycomb structural body 6, thethree requirements of weight reduction, securing panel rigidity, andsecuring dent resistance can be satisfied at a high level.

Note that, as long as the relative positional relationship between thejoints 4 illustrated in FIG. 13 is satisfied, a similar effect isobtained even if the arrangement of the joint 4 is changed. For example,the arrangement of the plurality of joints 4 as a whole in the thirdmodification illustrated in FIG. 13 may be symmetrically replaced in thevehicle width direction X.

Further, instead of the third modification illustrated in FIG. 13, thejoints 4 may be arranged in the form shown in a fourth modificationillustrated in FIG. 14. In FIG. 14, among the six side portions 10 ofthe unit 7, for example, the joint 4 is provided on the right front sideportion 10 b and the left rear side portion 10 e as two sides extendingin parallel with each other, and on two side portions 10 which are incontact with the two ends of either one of these two side portions 10 band 10 e. That is, the joint 4 is provided on four of the side portions10 in the unit 7. In this second modification, a first unit 21 as a setof the units 7 in which the joint 4 is not provided on the rear sideportion 10 d and the left front side portion 10 f, and a second unit 22as a set of the units 7 in which the joint 4 is not provided on thefront side portion 10 a and the right rear side portion 10 c areprovided. In the first unit 21, the units 7 extend in a row in thedirection from the left rear toward the right front. Similarly, in thesecond unit 22 the units 7 extend in a row in the direction from theleft rear toward the right front. Further, the first units 21 and thesecond units 22 are alternately arranged.

Note that, as long as the relative positional relationship between thejoints 4 illustrated in FIG. 14 is satisfied, a similar effect isobtained even if the arrangement of the joint 4 is changed. For example,the arrangement of the plurality of joints 4 as a whole in the fourthmodification illustrated in FIG. 14 may be symmetrically replaced in thevehicle width direction X.

In the third modification and the fourth modification described above, aform in which, in each unit 7, the joint 4 is provided in four of theside portions 10, and the joint 4 is not provided in two of the sideportions 10 is described as an example. However, the joints 4 need notbe arranged in this manner. For example, as illustrated in a fifthmodification in FIG. 15, in each unit 7, the joint 4 may be provided ontwo side portions 10 among the six side portions 10. That is, the joint4 is provided on a set of two of the side portions 10, 10 that face eachother in parallel in plan view. Further, the joint 4 is not provided onthe remaining four side portions 10, and therefore the remaining fourside portions 10 are directly adjacent to the panel 2.

In the fifth modification illustrated in FIG. 15, among the six sideportions 10 of the unit 7, for example, the joint 4 is provided only onthe right rear side portion 10 c and the left front side portion 10 fwhich extend in parallel with each other. Therefore, in each unit 7, thejoint 4 is not provided on four of the side portions 10. Thus, when aconfiguration is adopted in which, in each unit 7, the joint 4 isprovided on two of the side portions 10 (10 c, 10 f) which are some ofthe six side portions 10 and which are parallel with each other, thethree requirements of weight reduction, securing panel rigidity, andsecuring dent resistance can be satisfied at a high level.

Note that, instead of the fifth modification illustrated in FIG. 15, amodification (not illustrated in the drawings) in which, among the sixside portions 10, the joint 4 is provided on only the front side portion10 a and the rear side portion 10 d which are parallel with each other,and a modification (not illustrated in the drawings) in which, among thesix side portions 10, the joint 4 is provided on only the right frontside portion 10 b and the left rear side portion 10 e which are parallelwith each other can be given as examples of the arrangement of thejoints 4.

By adopting any one of the configurations according to the embodimentand the respective modifications that are described above with respectto the joints 4, improvement in the performance of the panel 2 (at leastimprovement of the panel rigidity and improvement of the dentresistance) and a reduction in the weight of the panel 2 can berealized.

Note that, in the embodiment and respective modifications that aredescribed above, in each side portion 10 on which the joint 4 isprovided, the joint 4 is not limited to a case in which the joint 4 isformed in a continuous linear shape, and the joint 4 may beintermittently arranged in dot shapes.

According to the automobile hood 1 of the present embodiment, withrespect to each side portion 10 on which the joint 4 is provided amongthe six side portions 10 of the unit 7, the side portion 10 is incontact with the joint 4 over a range of 20% or more of the side portion10 with regard to the direction in which the side portion 10 extends.According to this configuration, both the panel rigidity and the dentresistance of the panel 2 can be increased. In particular, if the joint4 is a linear shape that extends continuously on the side portion 10,both the panel rigidity and dent resistance of the panel 2 can beincreased more in comparison to a case where the joint 4 is provided ina dot shape at corner portions of the hexagon or a case where the joint4 is provided in a dot shape at the center of the side portion 10.

Further, according to the automobile hood 1 of the present embodiment,the sheet thickness t1 of the panel 2 made of a steel sheet is 0.6 mm orless. In a case where the sheet thickness t1 of the panel 2 is 0.6 mm orless in this way, the panel rigidity and dent resistance obtained fromthe rigidity of the panel 2 itself decrease extremely in comparison to acase where the sheet thickness t1 of the panel 2 is 0.65 mm or more.More specifically, the panel rigidity of the panel 2 depends on theYoung's modulus and the sheet thickness of the panel 2, and inparticular, changes with the square of the sheet thickness. If thedesign sheet thickness of the panel 2 formed of a steel sheet is changedfrom 0.65 mm to 0.6 mm, the panel rigidity that the panel 2 can secureby itself is reduced extremely. This reduction in rigidity isparticularly noticeable from the aspect of a sense of touch perceivedwhen the panel 2 is pressed by a human hand, which is a factor thatreduces the salability of the automobile. Thus, in relation to the panelrigidity of the panel 2 that is made of steel, a critical significanceexists with respect to the sheet thickness t1 being between 0.6 mm and0.65 mm. Further, in a case where a thin panel 2 having a sheetthickness t1 of 0.6 mm or less is used as in the present embodimentalso, by combining the reinforcing member 3 and the panel 2 forreinforcement and stiffening, as the automobile hood 1, panel rigidityand dent resistance that are approximately equal to a case where thesheet thickness t1 of the panel 2 is 0.65 mm can be secured. Moreover,since the sheet thickness t1 of the panel 2 is reduced, a reduction inthe weight of the automobile hood 1 can be achieved through the weightreduction of the panel 2.

In addition, if the panel 2 and the reinforcing member 3 are made ofsteel, there is an advantage from the view point of material cost incomparison to the panel and the reinforcing member that are made of analuminum alloy. Furthermore, in the case of an automobile hood made ofan aluminum alloy, the idea of securing panel rigidity with areinforcing member located below a panel has originally not existedheretofore. Further, because the Young's modulus of an aluminum alloy islow compared to the Young's modulus of steel, the rigidity of analuminum alloy is lower than the rigidity of steel. Therefore, in anautomobile hood that is made of an aluminum alloy, in order to securerigidity that is equivalent to the rigidity of the automobile hood 1made of steel, it is necessary to make the sheet thickness of themembers larger. Hence, in order to satisfy the requirements regardingboth panel rigidity and dent resistance in a panel that is made of analuminum alloy, the sheet thickness increases. Therefore, the viewpointof improving both the panel rigidity and the dent resistance whilereducing the sheet thickness of the panel 2 and the reinforcing member 3as in the present embodiment does not exist with respect to anautomobile hood that is made of an aluminum alloy. However, as describedabove, from the viewpoint of panel rigidity and dent resistance, a paneland a reinforcing member made of a steel sheet and a panel and areinforcing member made of an aluminum alloy sheet can be set tothicknesses such that equivalent performance is obtained. Therefore, inthe present embodiment, the panel 2 and the reinforcing member 3 may besteel sheets or may be aluminum alloy sheets.

An embodiment and modifications of the present disclosure have beendescribed above. However, the present disclosure is not limited to theabove embodiment and modifications. In the present disclosure, variouschanges are possible within the scope of the accompanying claims.

EXAMPLES

Geometric models of the automobile hoods 1 shown in the embodiment andmodifications were created on a computer using CAD (Computer AidedDesign) software. That is, the automobile hoods 1 having the panel 2,the reinforcing member 3 and the joint 4 were created on a computer. Thepanel rigidity and dent resistance were then evaluated by performing CAE(Computer Aided Engineering) analysis, that is, computer simulation,with respect to the geometric models of the automobile hood 1. Notethat, the characteristics of each part were as follows.

Panel 2: Made of a high-strength steel sheet of 590 MPa-class. Yieldstress=375 MPa, tensile strength=622 MPa, sheet thickness t1=0.4mm.

Reinforcing member 3: Made of a mild steel sheet. Yield stress=163 MPa,tensile strength=325 MPa, sheet thickness t2=0.3 mm.

Note that, the modulus of elasticity of the steel sheet was a Young'smodulus of 206 GPa, with a Poisson's ratio of 0.3.

For the present examples, Disclosure Examples 1 to 7 and ComparativeExamples 1 to 4 were prepared. With regard to these Disclosure Examples1 to 7 and Comparative Examples 1 to 4, the length L1 of one side of thehexagonal first ridge line 31, the corner width W11 of the upper face 11b of the floor 11, and the center width W12 of the upper face 11 b wereas shown in Table 1.

As illustrated in FIG. 16, shapes A and B (Present Disclosure Examples 1and 2) had the dodecagonal annular end part 20B. Shape C (ComparativeExample 1) had a hexagonal annular end part 20A′. The respective apexesof the annular end part 20A′ were disposed on the correspondingmidpoints of the six sides of the first ridge line 31. According to thisconfiguration, the center width W12 was zero mm. The annular end part20A of shape D (Present Disclosure Example 3) was arranged similarly tothe first ridge line 31 in plan view.

As illustrated in FIG. 17, shapes E and F (Present Disclosure Examples 4and 5) had the dodecagonal annular end part 20B. Shapes G and H(Comparative Examples 2 and 3) had a dodecagonal annular end part 20B′.In the annular end part 20B′, there were apexes AP1′ which were adjacentto the apexes of the first ridge line 31, and apexes AP2′ which wereadjacent to the midpoints of the first ridge line 31. Further, adistance DS2B′ from the center point P3 of the hexagonal first ridgeline 31 to each apex AP2′ was less than a distance DS1B′ from the centerpoint P3 to each apex APP. Furthermore, in the shapes G and H, one partof the annular end part 20B′ was located on the outer side of the firstcircle CR1. In addition, in the shapes G and H, the corner width W11 wasless than the center width W12 (W11<W12).

As illustrated in FIG. 18, shapes I, J and K (Present DisclosureExamples 6 and 7 and Comparative Example 4) had the circular annular endpart 20. In the shape K (Comparative Example 4), the annular end part20′″ was located on the inner side of the second circle CR2. In each ofPresent Disclosure Examples 1 to 7, the corresponding annular end part20, 20A or 20B was located between the first circle CR1 and the secondcircle CR2, and the width W1 of the upper face 11 b of the floor 11 was2 mm or more.

In the CAE analysis, a point C1 (see FIG. 3) on the center position ofthe unit 7, which is the weakest part of the panel 2, was set as a loadpoint, and a predetermined load P was applied to this load point. Theresults were used as the evaluations of the panel rigidity and the dentresistance.

[Panel Rigidity Evaluation Conditions]

The load P was set to 49 N when evaluating the panel rigidity. If themaximum value of the deflection of the panel 2 when 49 N was applied wasless than 1.8 mm, the relevant example was evaluated as “excellent”, ifthe maximum value was less than 2.0 mm, the example was evaluated as“good”, and if the maximum value was 2.0 mm or more, the example wasevaluated as “poor”.

[Dent Resistance Evaluation Conditions]

The load P was set to 245 N when evaluating the dent resistance. If themaximum value of the plastic deformation amount of the panel 2 when 245N was applied was less than 0.23 mm, the relevant example was evaluatedas “excellent”, if the maximum value was less than 0.35 mm, the examplewas evaluated as “good”, and if the maximum value was 0.35 mm or more,the example was evaluated as “poor”.

The evaluation results for panel rigidity and dent resistance,respectively, are shown in Table 1.

TABLE 1 Length of One Side of First Ridge Corner Center Weight of Shapeof Annular Line 31 Width W11 Width W12 Panel Dent Reinforcing End Part20 etc. (mm) (mm) (mm) Rigidity Resistance Member 3 RemarksA(Substantially 51 15 7.5 excellent good 3.2 kg Present DodecagonalShape) Disclosure Example 1 B(Substantially 51 15 5 excellent good 3.1kg Present Dodecagonal Shape) Disclosure Example 2 C(Substantially 5114.25 0 good poor 3.1 kg Comparative Hexagonal Shape) Example 1D(Substantially 51 11.55 10 good good 3.1 kg Present Hexagonal Shape)Disclosure Example 3 E(Substantially 51 10 5 good excellent 3.0 kgPresent Dodecagonal Shape) Disclosure Example 4 F(Substantially 51 102.5 good good 3.0 Kg Present Dodecagonal Shape) Disclosure Example 5G(Substantially 51 5 10 good poor 3.1 Kg Comparative Dodecagonal Shape)Example 2 H(Substantially 51 5 7.5 poor poor 3.0 Kg ComparativeDodecagonal Shape) Example 3 I(Substantially 51 10 2 good good 2.9 KgPresent Circular Shape) Disclosure Example 6 J(Substantially 51 14 6excellent good 3.1 Kg Present Circular Shape) Disclosure Example 7K(Substantially 51 26 18 excellent poor 3.6 Kg Comparative CircularShape) Example 4

As shown in Table 1, for Comparative Example 1, because the center widthW12 was zero, a support span of the panel 2 that could secure the panelrigidity was realized, however, because the deflection of the panel 2was too large, the dent resistance was evaluated as “poor”. Further, inComparative Examples 2 and 3, one part of the annular end part 20A′ wasdisposed outside the first circle CR1. Therefore, the distance betweenthe point of action of the load P and the annular end part 20B′(constraint position) became too long. As a result, localized stressarose at the point of action of the load P, and consequently a stressstate that was more than the yield load of the panel 2 was liable tooccur and a dent was liable to occur. That is, the dent resistance wasevaluated as “poor”. With regard to Comparative Example 3, the panelrigidity of the panel 2 was also evaluated as “poor”. With regard toComparative Example 4 the annular end part 20′″ was disposed inside thesecond circle CR2, and the support span of the panel 2 was short.Therefore, although the panel rigidity of the panel 2 was evaluated as“excellent”, localized stress arose at the point of action of the loadP, and as a result the dent resistance was evaluated as “poor”.

On the other hand, with regard to Present Disclosure Examples 1 to 7,because the annular end parts 20, 20A and 20B were set to appropriatevalues, the support span of the panel 2 was appropriate, and the tensionof the panel 2 could be sufficiently maintained and moderate deflectionof the panel 2 was allowed. As a result, a favorable result (“good” orbetter) was obtained with respect to both the panel rigidity and thedent resistance. In particular, in Present Disclosure Examples 1 and 2,a very favorable result (“excellent”) was obtained for panel rigidity,while also obtaining a favorable result (“good”) for dent resistance.Further, in Present Disclosure Example 4, a very favorable result(“excellent”) was obtained for dent resistance, while also obtaining afavorable result (“good”) for panel rigidity. Furthermore, in PresentDisclosure Example 7, a very favorable result (“excellent”) was obtainedfor panel rigidity, while also obtaining a favorable result (“good”) fordent resistance.

Note that, as described above, with respect to the panel 2 made of asteel sheet and the reinforcing member 3 made of a steel sheet, and thepanel 2 made of an aluminum alloy sheet and the reinforcing member 3made of an aluminum alloy sheet, by setting the respective sheetthicknesses of these components to thicknesses such that the respectiveperformances thereof from the viewpoint of panel rigidity and dentresistance are equivalent, similar panel rigidity and dent resistancecan be secured. Therefore, it is clear that similar advantageous effectscan also be obtained when the present invention is applied to analuminum alloy sheet.

Industrial Applicability

The present disclosure can be widely applied as an automobile hood.

REFERENCE SIGNS LIST

-   1 Automobile Hood-   2 Panel-   3 Reinforcing Member-   4 Joint-   7 Unit-   11 Floor-   11 b Upper Face (Floor Surface)-   12 Inclined wall-   13 Top Plate-   20, 20A, 20B Annular End Part-   31 First Ridge Line (Hexagonal Annular Ridge Line)-   CR1 First Circle-   CR2 Second Circle-   t1 Sheet Thickness of Panel-   W1 Width of Upper Face (Width of Floor Surface)-   W11 Corner Width (Distance Between Corner of Hexagonal Ridge Line    and Annular End Part)-   W12 Center Width (Distance Between Center of One End of Ridge Line    and Annular End Part)

1. An automobile hood, comprising: a panel, a reinforcing member, and ajoint that joins together the panel and the reinforcing member, wherein:the reinforcing member includes a structure formed from a plurality ofunits having a hexagonal annular shape disposed in a close-packedarrangement; the unit has a floor, an inclined wall, and a top plate;the floor is adjacent to the panel; the top plate and the panel areseparated from each other; the inclined wall is between the floor andthe top plate; a hexagonal annular ridge line of the unit is between thefloor and the inclined wall; the floor has an annular end part which iscentered on a center of the annular unit; all of the end part is betweena first circle which is inscribed within the ridge line, and a secondcircle which is concentric with the first circle and which has a radiusthat is 60% of a radius of the first circle; the floor includes a floorsurface as a face which faces the panel; and a width of the floorsurface is 2 mm or more over an entire area of the annular end part in acircumferential direction of the annular end part.
 2. The automobilehood according to claim 1, wherein: a distance between a corner of thehexagonal ridge line and the annular end part is greater than a distancebetween a center of one side of the ridge line and the annular end part.3. The automobile hood according to claim 1, wherein: the end part iscircular.
 4. The automobile hood according to claim 1, wherein: the endpart is hexagonal.
 5. The automobile hood according to claim 1, wherein:the end part is dodecagonal.
 6. The automobile hood according to claim1, wherein: the panel is a steel sheet, and a sheet thickness of thepanel is within a range of 0.35 mm to 0.60 mm.
 7. The automobile hoodaccording to claim 1, wherein: the panel is an aluminum alloy sheet, anda sheet thickness of the panel is within a range of 0.50 mm to 1.00 mm.